The graph, published by Dr Michael Mann and a team of climate scientists, was the first time the rapid increases in recent temperatures was charted.

It helped frame the modern environment movement, and illustrated how human emissions of Greenhouse Gases were warming the planet.

The graph showed global temperatures over the last thousand years, and how the warming in the last century was unprecedented.

The line has a gradual downward trajectory until the late 1800s – when the Industrial Revolution started the large-scale release of Greenhouse Gases into the atmosphere – at which point it rapidly increases.

The research, published in the peer-reviewed journal Nature Geoscience​, is based on 511 climate archives from around the world. All the data has been freely released.

It also dismissed the often-quoted "Medieval Warm Period" or "Little Ice Age" as local temperature fluctuations that had no global impact.

Sceptics use these as simple examples to prove that there were temperature variations in the past and there was a much hotter period.

They ignore the fact that these "hockey stick" graphs talk about an increase in global temperatures. All these minor trends also stopped with the recent accelerated warming period.

Generally, the last two millennia saw a general cooling trend, but "recent warming reversed the long-term cooling", it said.

Sipho Kings

Sipho Kings is the Mail & Guardian's environment reporter. Broken ecosystems, bad corporations and mean people are the order of the day. This means his shoes are caked in all sorts of dodgy material. Read more from Sipho Kings